The stator of a three-phase AC motor includes a stator core and coils with three-phase windings fitted in slots in this stator core. Moreover, the coil of each phase includes: a part being a coil side inserted in the corresponding slot; and a part being a coil end situated outside the slot.
Further, an inter-phase insulation paper sheet is inserted between the adjacent coil ends of different phases to provide insulation between these coil ends of the different phases. The inter-phase insulation paper sheet after inserted between the coil ends is fixed to the coil ends by being tied thereto with a lace (lacing).
As general, conventional inter-phase insulation paper sheets, there are a rectangular inter-phase insulation paper sheet 1 as shown in Part (a) of FIG. 12, an inter-phase insulation paper sheet 2 with one end side formed in a trapezoidal shape as shown in Part (b) of FIG. 12, and the like.
Moreover, Patent Documents 1 and 2 listed below disclose inter-phase insulation paper sheets with improvements for solving problems in the inter-phase insulation paper sheets 1 and 2 of these simple shapes. The inter-phase insulation paper sheet disclosed in Patent Document 1 is folded in a V shape so as to increase its strength against tear. The inter-phase insulation paper sheet disclosed in Patent Document 2 includes flat portions and folded portions, and uses the elasticity of the folded portions to absorb changes in the gaps between coil ends and thereby prevent displacement of the inter-phase insulation paper sheet after its insertion between the coil ends.